What is a Normal Sinus Rhythm?

The heart has a “rhythm” or set beat (like music) to pump blood between the four chambers of the heart. A normal heart works by sending a signal from the “sinus” node to the heart chambers.

Think of the sinus node as the on/off switch for the heart. The normal beating of the heart controlled by the sinus node is called “normal sinus rhythm.”

A machine called an “ECG” (aka “Electrocardiogram”) can measure the heart’s electrical impulses to see if it is pumping like normal. A normal ECG looks like this:

What is a Prolonged QT Interval?

A normal heart has a specific time period from one beat to another. These points in time are marked with P, Q, R, S, and T.

A problem with the heart can cause the time from point Q to point T to get longer. This is “Prolonged QT Interval.”

Risk Factors for QT Prolongation

Long QT syndrome is a condition which can be inherited or induced by drugs or abnormal levels of the salts normally found in the blood, such as potassium and magnesium.

How do I know if I haveQT Prolongation?

The gold standard for finding out whether you have long QT syndrome is the ECG. Although it is not routine, you can get a genetic test in some situations, particularly if you have a close relative with long QT syndrome. Up to half of people with long QT syndrome never have any signs or symptoms. For people who do experience signs and symptoms of long QT syndrome, the most common signs include fainting and seizures.

Why is QT Prolongation Important?

Many people can lead healthy, productive lives with QT Prolongation. However, some people can develop Torsades de Points (TdP), a French phrase meaning “twisting of the points.” In this condition, a person develops an irregular heart rhythm which is extremely dangerous and can lead to death!

This is an ECG of TdP:

Factors whichINCREASE YOUR RISK

of Developing TdP:

Slow heart rate Low Potassium level Low Magnesium level “Stimulant” conditions

• Exercise• Emotion• Use of drugs like dopamine,

epinephrine, or albuterol

Management of QT Prolongation Ask your doctor or pharmacist about

your medications and if they can cause QT Prolongation

Watch your diet to make sure that you are getting enough potassium and magnesium.

Natural sources of potassium include avocados, bananas, citrus fruits, lentils, milk, molasses, nuts, parsnips, potatoes, raisins, canned sardines, fresh spinach, yogurt, and wholegrain cereals.

Natural sources of magnesium

include nuts, legumes, wholegrain cereals and breads, soybeans, and seafoods. Dark green vegetables are good sources.

Never take any medications NOT prescribed by your doctor

Medications Associated withQT Prolongation

Drugs commonly involved:Disopyramide, Dofetilide, Ibutilide, Procainamide, Quinidine, Sotalol, Bepridil, Amiodarone

Drug classes commonly involved:

Cardiac: See Above

Anti-infective agents:

clarithromycin, erythromycin, halofantrine, pentamidine, sparfloxacin

Nausea/Vominting agents:

domperidone, droperidol

Antipsychotic agents:

chlorpromazine, haloperidol, mesoridazine, thioridazine, pimozide

Miscellaneous:

Arsenic trioxide, Cisapride, Lidoflazine, Methadone

For More Information:

www.torsades.orgPhone number

www.americanheart.org1-800-242-8721

www.mayoclinic.com480-301-8000

QT Prolongation

Presented by

Todd S. ReeseShannon Dye

PharmD CandidatesMidwestern University

Edited by

Dr. Mindy Throm, PharmDBanner Desert Medical Center